1. Technical Field
The present disclosure relates to a light emitting diode (LED) and, more particularly, to an LED capable of emitting two lights with different color temperatures at different times.
2. Description of Related Art
LEDs have been available since the early 1960's. Because of the relatively high light-emitting efficiency of LEDs, LED usage has been increased in popularity in a variety of applications, e.g., residential, traffic, commercial, industrial settings. With development of the semiconductor technology, nowadays LEDs could emit various colorful light, wherein white light is most preferable in general illumination for its color mostly similar to the sunshine. However, pure white light is not always popular in general illumination, sometimes the LEDs are designed to emit nonsolid white light for meeting particular color temperature requirements of some occasions. For example, orange-white light is more favorable in residential illumination for its warm color, while blue-white light could refresh people so it is widely used in office illumination.
The LED die included in the LED determines which color the light emitted from the LED could have. Typically, an LED could only emit white light with a single color temperature. If a lamp needs to produce two lights with different color temperatures, a lager number of the LEDs have to be used in the lamp for ensuring sufficient intensity under each color temperature. Therefore, a multichip LED technology is developed in order to reduce the total number of the LEDs used in the lamp. The multichip LED includes multiple LED dies capable of emitting lights with different colors, whereby only less multichip LEDs can satisfy different color temperature requirements without reduction in intensity of the lamp.
The multichip LED generally employs three different LED dies, i.e., a Red LED die, a Green LED die and a Blue LED die (RGB), to obtain the white light. The three LED dies are independently controllable to adjust the brightness of each LED die, whereby the resultant white light blended by the red, green and blue lights from the three LED dies, could be flexibly switched between different color temperatures.
The brightness of the three LED dies of the multichip LED depends on the current input thereto. In order to regulate the current input to each LED die to further vary the brightness thereof, a process is needed to couple with the multichip LED to thereby assign each LED die with a target current. However, since the process is relatively expensive, the cost of the lamp having the multichip LEDs is raised unexpectedly.
What is needed, therefore, is an LED which can overcome the above-mentioned disadvantages.